As a web developer, I understand the need to allow users to create content. However, I consider full blown web-based WYSIWYGs (such as TinyMCE and CK Editor) to be terrible tools. Yes, they take care of most of the dirty details, but they also have the capacity produce bloated garbage markup. I've always found bbCode annoying. I've used a couple of Wiki syntaxes as well (MediaWiki, Jira), and find them only slightly less annoying than bbCode. Because I know HTML, I prefer to just write HTML when I know the final format will be HTML.
Markdown syntax is clean, succinct, and can be extended when needed. The vast majority of non-savvy users only need to do basic formatting (bold, italics, headlines, lists) and Markdown covers that very well, in a way that the user can't do much damage to the prescribed styling of the content.
I've very briefly experimented with LaTEX, not enough to have actually used it for anything. I was not aware of PanDoc, but it looks very interesting.